Hard alloy surface high-temperature-resistant protective coating and preparation process thereof

Abstract

The invention provides a hard alloy surface high-temperature-resistant protective coating and a preparation process thereof, and belongs to the field of superhard materials. The preparation process comprises the following steps: cleaning the hard alloy; etching and carrying out microwave plasma decarburization; diborane is pumped in for surface boronizing; sputtering and depositing a tantalum layer on the surface and performing reverse sputtering; and controlling the methane flow and carrying out chemical vapor deposition on the four-layer diamond coating. According to the method, the pretreated hard alloy is placed in vacuum tube furnace equipment, mixed gas of hydrogen and diborane is pumped into the vacuum tube furnace equipment for surface boronizing, then the hard alloy is placed in a plasma surface alloying furnace for surface sputtering deposition of a tantalum layer, and after reverse sputtering, four layers of diamond coatings are deposited through a chemical vapor deposition method. The prepared high-temperature-resistant protective coating on the surface of the hard alloy not only has better high-temperature resistance and corrosion resistance, but also has excellent adhesive force and wear resistance, so that the effect of prolonging the service life of the hard alloy is achieved.

Description

Technical Field

[0001] The invention relates to the field of superhard materials, and in particular to a high-temperature resistant protective coating on the surface of a cemented carbide and a preparation process thereof. Background Art

[0002] Cemented carbide is an alloy material made of hard compounds of refractory metals and bonding metals through powder metallurgy. It is widely used as tool materials such as turning tools, milling cutters and drills due to its high hardness, good wear resistance and good high-temperature working performance. However, traditional cemented carbide tools are prone to sticking, cutting deformation and abrasive wear when processing certain special materials at high speed. Diamond film has the characteristics of high hardness, good wear resistance and high temperature resistance and is considered to be an ideal tool coating. Since diamond film can be directly deposited on the base material, it has the advantage of being used in tools with complex shapes.

[0003] However, when the substrate is WC-Co cemented carbide, after the diamond film is deposited on its surface, the interface between the diamond film and the cemented carbide is poorly bonded due to the formation of non-diamond carbon catalyzed by cobalt at the interface between the diamond and the cemented carbide, resulting in poor adhesion of the diamond film, which seriously affects the service life of the protective coating. In addition, although the existing micron diamond film has strong adhesion, its surface roughness is relatively high, which easily leads to an increase in the wear rate of the diamond-coated tool, affecting the machining accuracy and surface quality of the workpiece. Although the nano diamond film has a smooth surface and good surface quality, its adhesion to the complex-shaped substrate is poor, causing the tool coating to fall off easily.

[0004] Therefore, we proposed a high-temperature resistant protective coating on the surface of cemented carbide with excellent adhesion and wear resistance and its preparation process to extend the service life of the workpiece. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a high temperature resistant protective coating on the surface of cemented carbide and a preparation process thereof.

[0006] A preparation process of a high temperature resistant protective coating on a cemented carbide surface comprises the following steps: S1: Cleaning carbide, The YG type cemented carbide was immersed in acetone, deionized water and anhydrous ethanol in turn, and ultrasonically cleaned respectively to obtain a three-times cleaned alloy; S2: Etching and microwave plasma decarburization, The alloy cleaned three times is sequentially soaked in the first soaking liquid and the second soaking liquid for etching, and then subjected to surface sandblasting and microwave plasma decarburization to obtain a surface pretreated alloy; S3: Pump in diborane for surface boronization, Mixing hydrogen and diborane to form a boron-containing gas, then placing the surface pretreated alloy in a vacuum tube furnace, introducing the boron-containing gas, heating and pressurizing, and performing surface boriding to obtain a surface borided alloy; S4: Surface sputtering deposition of tantalum layer and reverse sputtering, The surface boride alloy is placed in a plasma surface alloying furnace, and a tantalum layer is sputtered and deposited on the surface of the surface boride alloy under heating and power supply conditions, and then reverse sputtering is performed to obtain a thin tantalum layer alloy; S5: Control the methane flow and chemically vapor deposit four layers of diamond coating, The thin tantalum layer alloy is placed in an acetone dispersion of diamond for ultrasonic oscillation, then ultrasonically cleaned with an ethanol solution, and then four layers of diamond coating are deposited on the surface of the thin tantalum layer alloy by chemical vapor deposition by controlling the methane flow rate to obtain a high-temperature resistant protective coating.

[0007] Furthermore, the cleaning of cemented carbide in step S1 specifically comprises the following steps: S1.1: Place the YG cemented carbide in an ultrasonic cleaning machine, add acetone to the ultrasonic cleaning machine until the YG cemented carbide is completely immersed, then start the ultrasonic cleaning machine and perform ultrasonic cleaning for 10-20 minutes to obtain a cleaned alloy; S1.2: Open the liquid outlet assembly of the ultrasonic cleaning machine, discharge the acetone, and then add deionized water to the ultrasonic cleaning machine until the primary cleaning alloy is completely immersed, and continue ultrasonic cleaning for 10-20 minutes to obtain a secondary cleaning alloy; S1.3: Open the liquid outlet assembly of the ultrasonic cleaning machine, discharge the deionized water, and then add anhydrous ethanol to the ultrasonic cleaning machine until the secondary cleaning alloy is completely immersed, and ultrasonically clean for 20-30 minutes to obtain the tertiary cleaning alloy.

[0008] Furthermore, the etching and microwave plasma decarburization in step S2 specifically includes the following steps: S2.1: placing the three-cleaned alloy obtained in step S1.3 in a soaking box, then pouring the first soaking liquid into the soaking box, soaking for 10-20 minutes, and performing an etching to obtain a first-etched alloy; S2.2: Open the liquid outlet valve of the immersion box to discharge the first immersion liquid, then pour the second immersion liquid into the immersion box, let it stand and soak for 10-20 minutes, and perform secondary etching on the above-mentioned primary etched alloy to obtain a secondary etched alloy; S2.3: Rinse the secondary etched alloy with deionized water for 2-3 minutes, and then sandblast the surface with diamond powder to obtain a textured alloy; S2.4: Place the above-mentioned textured alloy in a microwave chemical vapor deposition device, adjust the microwave power to 500-600W and the mixed gas pressure in the reaction chamber to 2-3kPa, etch the textured alloy for 1-2h for decarburization treatment, and obtain a surface pretreated alloy.

[0009] Further, step S3 of pumping diborane to perform surface boronization specifically includes the following steps: S3.1: Using a first gas pump to measure hydrogen, and using a second gas pump to measure diborane, then pumping the hydrogen and diborane into a mixing box at a volume ratio of 16-20:1 through the first gas pump and the second gas pump, and mixing them thoroughly to obtain a boron-containing gas; S3.2: placing the surface pretreated alloy obtained in step S2.4 in a vacuum tube furnace device, and then passing the boron-containing gas in the mixing box into the vacuum tube furnace device through the air inlet valve until the air pressure sensor in the vacuum tube furnace device detects that the air pressure in the furnace reaches 10-12 kPa; S3.3: Start the vacuum tube furnace equipment, heat the surface pretreated alloy at a temperature of 1000-1200° C. for 1-2 hours, and perform surface boriding on the surface pretreated alloy to obtain a surface borided alloy.

[0010] Furthermore, the surface sputtering deposition of the tantalum layer and reverse sputtering in step S4 specifically includes the following steps: S4.1: placing the surface borided alloy obtained in step S3.3 in a plasma surface alloying furnace, and introducing argon gas into the furnace until all the air in the furnace is exhausted; S4.2: adjusting the heating temperature of the plasma surface alloying furnace to 800-900°C, the working voltage of the anode and cathode to 300-400V, and the working voltage of the source electrode to 600-750V; S4.3: starting the plasma surface alloying furnace, under the bombardment of argon ions, the source electrode sputters out tantalum ions, and deposits them on the surface of the surface boride alloy to obtain a thick tantalum alloy layer; S4.4: Adjust the working voltage of the anode and cathode to 600-750V and the working voltage of the source electrode to 300-450V, and start the plasma surface alloying furnace again. Under the action of the high voltage electric field, the argon ions move and bombard the surface of the thick tantalum layer alloy, and reverse sputter to obtain a thin tantalum layer alloy.

[0011] Furthermore, step S5 of controlling the methane flow and chemically vapor depositing four layers of diamond coating specifically includes the following steps: S5.1: placing the thin tantalum alloy layer obtained in step S4.4 in a diamond acetone dispersion, ultrasonically vibrating for 30-40 minutes, and then placing it in an ethanol solution and ultrasonically cleaning for 3-5 minutes to obtain a prefabricated coating alloy; S5.2: placing the above prefabricated coating alloy in a chemical vapor deposition device, adjusting the hydrogen flow rate to 800-1000 mL / min, the heating temperature to 850-900°C and the methane flow rate to 20-25 mL / min, and depositing for 2-3 hours to obtain a single-layer diamond coating; S5.3: Keeping other conditions unchanged, adjust the methane flow rate to 25-30 mL / min, and continue deposition for 1-2 h to obtain a double-layer diamond coating; S5.4: Keeping other conditions unchanged, adjust the methane flow rate to 20-25 mL / min, and continue deposition for 2-3 h to obtain a three-layer diamond coating; S5.5: Keep other conditions unchanged, adjust the methane flow rate to 25-30 mL / min, and continue deposition for 1-2 hours to obtain a high temperature resistant protective coating.

[0012] Furthermore, the first soaking liquid is prepared by mixing potassium ferrocyanide, potassium hydroxide and deionized water in a mass ratio of 1:1:18-20, the second soaking liquid is prepared by mixing hydrochloric acid and hydrogen peroxide in a volume ratio of 1:4-6, and the mixed gas is a mixture of argon and hydrogen.

[0013] Furthermore, during the high-temperature boronizing process of the vacuum tube furnace equipment, when the air pressure sensor detects that the air pressure in the furnace is lower than 10kPa, the air pressure sensor sends a start signal to the controller. After the controller receives the start signal sent by the air pressure sensor, it controls the air intake valve to open and replenishes boron-containing gas into the vacuum tube furnace equipment until the air pressure sensor detects that the air pressure in the vacuum tube furnace equipment reaches 10-12kPa. The air pressure sensor sends a stop signal to the controller. When the controller receives the stop signal sent by the air pressure sensor, it controls the air intake valve to close and stops replenishing boron-containing gas. This cycle is continued to maintain the internal air pressure of the vacuum tube furnace stable.

[0014] Furthermore, the total thickness of the diamond coating is 3-3.4 μm.

[0015] Furthermore, a high temperature resistant protective coating on the surface of cemented carbide is prepared by the preparation process of a high temperature resistant protective coating on the surface of cemented carbide described in any one of the above items.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The present invention places the pretreated cemented carbide in a vacuum tube furnace and pumps a mixed gas of hydrogen and diborane into the surface for boronizing, and then places the pretreated cemented carbide in a plasma surface alloying furnace for sputtering and depositing a tantalum layer on the surface. After reverse sputtering, four layers of diamond coating are deposited by chemical vapor deposition. The high-temperature resistant protective coating on the surface of the cemented carbide not only has good high-temperature resistance and corrosion resistance, but also has excellent adhesion and wear resistance, thereby achieving the effect of extending the service life of the cemented carbide.

[0017] 2. Before chemical vapor deposition of diamond coating on the surface of cemented carbide, the present invention first uses diborane gas to perform vacuum hot boronization treatment on the pre-treated cemented carbide surface, so as to generate Co-WB phase on the cemented carbide surface to prevent Co from diffusing into the diamond coating, thereby preventing Co from catalyzing the formation of non-diamond carbon at the interface between diamond and cemented carbide and affecting the interface and bonding force between diamond and cemented carbide, thereby achieving the effect of improving the adhesion of the diamond coating.

[0018] 3. The present invention deposits a tantalum layer on the surface of the boronized layer after the boronizing treatment on the surface of the cemented carbide to further inhibit the diffusion of Co into the diamond coating. In addition, micropores can be formed on the surface of the tantalum layer through the reverse sputtering process, thereby improving the adhesion of the diamond coating to the tantalum layer, thereby achieving the effect of further improving the adhesion of the diamond coating.

[0019] 4. The present invention gradually adjusts the methane flow rate, and the four-layer micro-nano composite diamond coating prepared on the surface of the tantalum layer by chemical vapor deposition has high wear resistance and good adhesion, which can improve the poor adhesion of the single-layer nano diamond coating and the high wear problem caused by the rough surface of the single-layer micron diamond coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art to make and use the present disclosure.

[0021] Figure 1 This is a flow chart of the preparation process of the high temperature resistant protective coating on the surface of cemented carbide used in the embodiment of the present invention.

[0022] Figure 2 The following is a summary table of the performance test results of Examples 1-3 and Comparative Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0023] The following is a detailed description of a high temperature resistant protective coating on a cemented carbide surface and its preparation process provided by the present invention in combination with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternative methods to implement some known technologies; and the accompanying drawings are only for a more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0024] Example 1: A process for preparing a high temperature resistant protective coating on a hard alloy surface, such as Figure 1 As shown, the following steps are included: S1: Cleaning carbide, Place the YG type cemented carbide in an ultrasonic cleaning machine, and add acetone to the ultrasonic cleaning machine until the YG type cemented carbide is completely immersed, then start the ultrasonic cleaning machine, perform ultrasonic cleaning for 10 minutes, and obtain a first-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the acetone, and then add deionized water to the ultrasonic cleaning machine until the first-cleaned alloy is completely immersed, continue ultrasonic cleaning for 10 minutes, and obtain a second-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the deionized water, and then add anhydrous ethanol to the ultrasonic cleaning machine until the second-cleaned alloy is completely immersed, and perform ultrasonic cleaning for 20 minutes to obtain a third-cleaned alloy; S2: Etching and microwave plasma decarburization, The alloy cleaned three times is placed in a soaking box, and then a first soaking solution prepared by mixing potassium ferrocyanide, potassium hydroxide and deionized water in a mass ratio of 1:1:18 is poured into the soaking box, and the alloy is allowed to stand for 10 minutes, and an etching is performed once to obtain a first-etched alloy. Then, the liquid outlet valve of the soaking box is opened to discharge the first soaking solution, and then a second soaking solution prepared by mixing hydrochloric acid and hydrogen peroxide in a volume ratio of 1:4 is poured into the soaking box, and the alloy is allowed to stand for 10 minutes, and the first-etched alloy is etched twice to obtain a second-etched alloy. The second-etched alloy is then rinsed with deionized water for 2 minutes, and then the surface is sandblasted with diamond powder to obtain a textured alloy. Subsequently, the textured alloy is placed in a microwave chemical vapor deposition device, and the microwave power is adjusted to 500 W and the pressure of the mixed gas formed by mixing argon and hydrogen in the reaction chamber is adjusted to 2 kPa. The textured alloy is etched for 1 hour for decarburization treatment to obtain a surface pretreated alloy. S3: Pump in diborane for surface boronization, A first air pump is used to measure hydrogen, and a second air pump is used to measure diborane. The hydrogen and diborane are then pumped into a mixing box at a volume ratio of 16:1 through the first air pump and the second air pump to be fully mixed to obtain a boron-containing gas. The surface pretreated alloy is then placed in a vacuum tube furnace device. The boron-containing gas in the mixing box is passed into the vacuum tube furnace device through an air inlet valve until an air pressure sensor in the vacuum tube furnace device detects that the air pressure in the furnace reaches 10 kPa. The vacuum tube furnace device is started, and the surface pretreated alloy is heated at a temperature of 1000° C. for 1 hour to perform surface boronization on the surface to obtain a surface boron compound. Gold, during the high-temperature boronizing process of the vacuum tube furnace equipment, when the air pressure sensor detects that the air pressure in the furnace is lower than 10kPa, the air pressure sensor sends a start signal to the controller. After the controller receives the start signal sent by the air pressure sensor, it controls the air intake valve to open and replenishes the boron-containing gas into the vacuum tube furnace equipment, until the air pressure sensor detects that the air pressure in the vacuum tube furnace equipment reaches 10kPa, the air pressure sensor sends a stop signal to the controller. When the controller receives the stop signal sent by the air pressure sensor, it controls the air intake valve to close and stops replenishing the boron-containing gas, and this cycle continues to maintain the internal air pressure of the vacuum tube furnace stable; S4: Surface sputtering deposition of tantalum layer and reverse sputtering, The surface borided alloy is placed in a plasma surface alloying furnace, and argon gas is introduced into the furnace until the air in the furnace is exhausted, the heating temperature of the plasma surface alloying furnace is adjusted to 800° C., the working voltages of the anode and the cathode are adjusted to 300V, and the working voltage of the source electrode is adjusted to 600V, and then the plasma surface alloying furnace is started. Under the bombardment of argon ions, tantalum ions are sputtered from the source electrode and deposited on the surface of the surface borided alloy to obtain a thick tantalum layer alloy. Subsequently, the working voltages of the anode and the cathode are adjusted to 600V, and the working voltage of the source electrode is adjusted to 300V, and the plasma surface alloying furnace is started again. Under the action of the high voltage electric field, the argon ions move and bombard the surface of the thick tantalum layer alloy, and reverse sputtering is performed to obtain a thin tantalum layer alloy; S5: Control the methane flow and chemically vapor deposit four layers of diamond coating, The above-mentioned thin tantalum layer alloy is placed in an acetone dispersion of diamond, ultrasonically vibrated for 30 minutes, and then placed in an ethanol solution and ultrasonically cleaned for 3 minutes to obtain a pre-coated alloy. The pre-coated alloy is then placed in a chemical vapor deposition device, the hydrogen flow rate is adjusted to 800 mL / min, the heating temperature is 850°C and the methane flow rate is 20 mL / min, and deposition is performed for 2 hours to obtain a single-layer diamond coating. Subsequently, while keeping other conditions unchanged, the methane flow rate is adjusted to 25 mL / min, and deposition is continued for 1 hour to obtain a double-layer diamond coating. While keeping other conditions unchanged, the methane flow rate is adjusted to 20 mL / min, and deposition is continued for 2 hours to obtain a three-layer diamond coating. While keeping other conditions unchanged, the methane flow rate is adjusted to 25 mL / min, and deposition is continued for 1 hour to obtain a high-temperature resistant protective coating, wherein the total thickness of the diamond coating is about 3 μm.

[0025] Performance Test: Firstly, the friction and wear properties of the prepared high temperature resistant protective coating were tested using a reciprocating friction and wear tester, wherein a silicon nitride ball with a diameter of 6 mm was used as a grinding pair. During the friction test, the silicon nitride ball remained fixed, the normal load was 15 N, the reciprocating frequency was 3 Hz, the reciprocating friction stroke was 10 mm, and the test duration was 60 min. The friction coefficient was automatically recorded during the experiment, and then the wear rate of the high temperature resistant protective coating was calculated according to the formula: wear rate = wear volume / (normal load × total sliding stroke). The results are shown in Figure 2. Figure 2 As shown; Then, the adhesion of the prepared high temperature resistant protective coating was tested using a scratch tester. The test parameters were: load pressure 0-100N, load speed 100N / min, scratch rate 1mm / min, scratch length 1mm. The adhesion results are as follows: Figure 2 shown.

[0026] Example 2: A process for preparing a high temperature resistant protective coating on a hard alloy surface, such as Figure 1 As shown, the following steps are included: S1: Cleaning carbide, Place the YG type cemented carbide in an ultrasonic cleaning machine, and add acetone to the ultrasonic cleaning machine until the YG type cemented carbide is completely immersed, then start the ultrasonic cleaning machine, perform ultrasonic cleaning for 15 minutes, and obtain a first-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the acetone, and then add deionized water to the ultrasonic cleaning machine until the first-cleaned alloy is completely immersed, continue ultrasonic cleaning for 15 minutes, and obtain a second-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the deionized water, and then add anhydrous ethanol to the ultrasonic cleaning machine until the second-cleaned alloy is completely immersed, and perform ultrasonic cleaning for 25 minutes to obtain a third-cleaned alloy; S2: Etching and microwave plasma decarburization, The alloy cleaned three times is placed in a soaking box, and then a first soaking solution prepared by mixing potassium ferrocyanide, potassium hydroxide and deionized water in a mass ratio of 1:1:19 is poured into the soaking box, and the mixture is allowed to stand for 15 minutes, and an etching is performed once to obtain a first-etched alloy, and then the liquid outlet valve of the soaking box is opened to discharge the first soaking solution, and then a second soaking solution prepared by mixing hydrochloric acid and hydrogen peroxide in a volume ratio of 1:5 is poured into the soaking box, and the mixture is allowed to stand for 15 minutes, and the first-etched alloy is etched twice to obtain a second-etched alloy, and then the second-etched alloy is rinsed with deionized water for 2.5 minutes, and then the surface is sandblasted with diamond powder to obtain a textured alloy, and then the textured alloy is placed in a microwave chemical vapor deposition device, and the microwave power is adjusted to 550W and the pressure of the mixed gas formed by mixing argon and hydrogen in the reaction chamber is adjusted to 2.5kPa, and the textured alloy is etched for 1.5 hours for decarburization treatment to obtain a surface pretreated alloy; S3: Pump in diborane for surface boronization, The first gas pump is used to measure hydrogen, and the second gas pump is used to measure diborane. The hydrogen and diborane are then pumped into a mixing box at a volume ratio of 18:1 through the first gas pump and the second gas pump to be fully mixed to obtain a boron-containing gas. The surface pretreated alloy is then placed in a vacuum tube furnace device. The boron-containing gas in the mixing box is passed into the vacuum tube furnace device through an air inlet valve until the air pressure sensor in the vacuum tube furnace device detects that the air pressure in the furnace reaches 11 kPa. The vacuum tube furnace device is started, and the surface pretreated alloy is heated at a temperature of 1100° C. for 1.5 hours to perform surface boronization on the surface pretreated alloy to obtain a surface boronized alloy. Alloy, during the high-temperature boronizing process of the vacuum tube furnace equipment, when the air pressure sensor detects that the air pressure in the furnace is lower than 10kPa, the air pressure sensor sends a start signal to the controller. After the controller receives the start signal sent by the air pressure sensor, it controls the air intake valve to open and replenishes the boron-containing gas into the vacuum tube furnace equipment, until the air pressure sensor detects that the air pressure in the vacuum tube furnace equipment reaches 11kPa, the air pressure sensor sends a stop signal to the controller. When the controller receives the stop signal sent by the air pressure sensor, it controls the air intake valve to close and stops replenishing the boron-containing gas, and the cycle continues to maintain the internal air pressure of the vacuum tube furnace stable; S4: Surface sputtering deposition of tantalum layer and reverse sputtering, The surface borided alloy is placed in a plasma surface alloying furnace, and argon gas is introduced into the furnace until the air in the furnace is exhausted, and the heating temperature of the plasma surface alloying furnace is adjusted to 850° C., the working voltages of the anode and the cathode are adjusted to 350V, and the working voltage of the source electrode is adjusted to 675V, and then the plasma surface alloying furnace is started. Under the bombardment of argon ions, tantalum ions are sputtered from the source electrode and deposited on the surface of the surface borided alloy to obtain a thick tantalum layer alloy. Subsequently, the working voltages of the anode and the cathode are adjusted to 675V, and the working voltage of the source electrode is adjusted to 375V, and the plasma surface alloying furnace is started again. Under the action of the high voltage electric field, the argon ions move and bombard the surface of the thick tantalum layer alloy, and reverse sputtering is performed to obtain a thin tantalum layer alloy; S5: Control the methane flow and chemically vapor deposit four layers of diamond coating, The above-mentioned thin tantalum layer alloy is placed in an acetone dispersion of diamond, ultrasonically vibrated for 35 minutes, and then placed in an ethanol solution and ultrasonically cleaned for 4 minutes to obtain a pre-coated alloy. The pre-coated alloy is then placed in a chemical vapor deposition device, the hydrogen flow rate is adjusted to 900 mL / min, the heating temperature is 875°C and the methane flow rate is 22.5 mL / min, and the deposition is performed for 2.5 hours to obtain a single-layer diamond coating. Subsequently, while keeping other conditions unchanged, the methane flow rate is adjusted to 27.5 mL / min, and the deposition is continued for 1.5 hours to obtain a double-layer diamond coating. While keeping other conditions unchanged, the methane flow rate is adjusted to 22.5 mL / min, and the deposition is continued for 2.5 hours to obtain a three-layer diamond coating. While keeping other conditions unchanged, the methane flow rate is adjusted to 27.5 mL / min, and the deposition is continued for 1.5 hours to obtain a high-temperature resistant protective coating, wherein the total thickness of the diamond coating is approximately 3.2 μm.

[0027] Performance Test: Firstly, the friction and wear properties of the prepared high temperature resistant protective coating were tested using a reciprocating friction and wear tester, wherein a silicon nitride ball with a diameter of 6 mm was used as a grinding pair. During the friction test, the silicon nitride ball remained fixed, the normal load was 15 N, the reciprocating frequency was 3 Hz, the reciprocating friction stroke was 10 mm, and the test duration was 60 min. The friction coefficient was automatically recorded during the experiment, and then the wear rate of the high temperature resistant protective coating was calculated according to the formula: wear rate = wear volume / (normal load × total sliding stroke). The results are shown in Figure 2. Figure 2 As shown; Then, the adhesion of the prepared high temperature resistant protective coating was tested using a scratch tester. The test parameters were: load pressure 0-100N, load speed 100N / min, scratch rate 1mm / min, scratch length 1mm. The adhesion results are as follows: Figure 2 shown.

[0028] Example 3: A process for preparing a high temperature resistant protective coating on a hard alloy surface, such as Figure 1 As shown, the following steps are included: S1: Cleaning carbide, Place the YG type cemented carbide in an ultrasonic cleaning machine, and add acetone to the ultrasonic cleaning machine until the YG type cemented carbide is completely immersed, then start the ultrasonic cleaning machine, perform ultrasonic cleaning for 20 minutes, and obtain a first-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the acetone, and then add deionized water to the ultrasonic cleaning machine until the first-cleaned alloy is completely immersed, continue ultrasonic cleaning for 20 minutes, and obtain a second-cleaned alloy, then open the liquid outlet component of the ultrasonic cleaning machine, discharge the deionized water, and then add anhydrous ethanol to the ultrasonic cleaning machine until the second-cleaned alloy is completely immersed, and perform ultrasonic cleaning for 30 minutes to obtain a third-cleaned alloy; S2: Etching and microwave plasma decarburization, The alloy cleaned three times is placed in a soaking box, and then a first soaking solution prepared by mixing potassium ferrocyanide, potassium hydroxide and deionized water in a mass ratio of 1:1:20 is poured into the soaking box, and the alloy is allowed to stand for 20 minutes, and an etching is performed once to obtain a first-etched alloy, and then the liquid outlet valve of the soaking box is opened to discharge the first soaking solution, and then a second soaking solution prepared by mixing hydrochloric acid and hydrogen peroxide in a volume ratio of 1:6 is poured into the soaking box, and the alloy is allowed to stand for 20 minutes, and the first-etched alloy is etched twice to obtain a second-etched alloy, and then the second-etched alloy is rinsed with deionized water for 3 minutes, and then the surface is sandblasted with diamond powder to obtain a textured alloy, and then the textured alloy is placed in a microwave chemical vapor deposition device, and the microwave power is adjusted to 600W and the pressure of the mixed gas formed by mixing argon and hydrogen in the reaction chamber is adjusted to 3kPa, and the textured alloy is etched for 2 hours for decarburization to obtain a surface pretreated alloy; S3: Pump in diborane for surface boronization, A first air pump is used to measure hydrogen, and a second air pump is used to measure diborane. The hydrogen and diborane are then pumped into a mixing box at a volume ratio of 20:1 through the first air pump and the second air pump to be fully mixed to obtain a boron-containing gas. The surface pretreated alloy is then placed in a vacuum tube furnace device. The boron-containing gas in the mixing box is passed into the vacuum tube furnace device through an air inlet valve until an air pressure sensor in the vacuum tube furnace device detects that the air pressure in the furnace reaches 12 kPa. The vacuum tube furnace device is started, and the surface pretreated alloy is heated at a temperature of 1200° C. for 2 hours to perform surface boronization on the surface to obtain a surface boron compound. Gold, during the high-temperature boronizing process of the vacuum tube furnace equipment, when the air pressure sensor detects that the air pressure in the furnace is lower than 10kPa, the air pressure sensor sends a start signal to the controller. After the controller receives the start signal sent by the air pressure sensor, it controls the air intake valve to open and replenishes the boron-containing gas into the vacuum tube furnace equipment, until the air pressure sensor detects that the air pressure in the vacuum tube furnace equipment reaches 12kPa, the air pressure sensor sends a stop signal to the controller. When the controller receives the stop signal sent by the air pressure sensor, it controls the air intake valve to close and stops replenishing the boron-containing gas, and this cycle continues to maintain the internal air pressure of the vacuum tube furnace stable; S4: Surface sputtering deposition of tantalum layer and reverse sputtering, The surface borided alloy is placed in a plasma surface alloying furnace, and argon gas is introduced into the furnace until the air in the furnace is exhausted, the heating temperature of the plasma surface alloying furnace is adjusted to 900° C., the working voltages of the anode and the cathode are adjusted to 400V, and the working voltage of the source electrode is adjusted to 750V, and then the plasma surface alloying furnace is started. Under the bombardment of argon ions, tantalum ions are sputtered from the source electrode and deposited on the surface of the surface borided alloy to obtain a thick tantalum layer alloy. Subsequently, the working voltages of the anode and the cathode are adjusted to 750V, and the working voltage of the source electrode is adjusted to 450V, and the plasma surface alloying furnace is started again. Under the action of the high voltage electric field, the argon ions move and bombard the surface of the thick tantalum layer alloy, and reverse sputtering is performed to obtain a thin tantalum layer alloy; S5: Control the methane flow and chemically vapor deposit four layers of diamond coating, The above-mentioned thin tantalum layer alloy is placed in an acetone dispersion of diamond, ultrasonically vibrated for 40 minutes, and then placed in an ethanol solution and ultrasonically cleaned for 5 minutes to obtain a pre-coated alloy. The pre-coated alloy is then placed in a chemical vapor deposition device, the hydrogen flow rate is adjusted to 1000 mL / min, the heating temperature is 900°C and the methane flow rate is 25 mL / min, and deposition is performed for 3 hours to obtain a single-layer diamond coating. Subsequently, while keeping other conditions unchanged, the methane flow rate is adjusted to 30 mL / min, and deposition is continued for 2 hours to obtain a double-layer diamond coating. While keeping other conditions unchanged, the methane flow rate is adjusted to 25 mL / min, and deposition is continued for 3 hours to obtain a three-layer diamond coating. While continuing to keep other conditions unchanged, the methane flow rate is adjusted to 30 mL / min, and deposition is continued for 2 hours to obtain a high-temperature resistant protective coating, wherein the total thickness of the diamond coating is 3.4 μm.

[0029] Performance Testing: Firstly, the friction and wear properties of the prepared high temperature resistant protective coating were tested using a reciprocating friction and wear tester, wherein a silicon nitride ball with a diameter of 6 mm was used as a grinding pair. During the friction test, the silicon nitride ball remained fixed, the normal load was 15 N, the reciprocating frequency was 3 Hz, the reciprocating friction stroke was 10 mm, and the test duration was 60 min. The friction coefficient was automatically recorded during the experiment, and then the wear rate of the high temperature resistant protective coating was calculated according to the formula: wear rate = wear volume / (normal load × total sliding stroke). The results are shown in Figure 2. Figure 2 As shown; Then, the adhesion of the prepared high temperature resistant protective coating was tested using a scratch tester. The test parameters were: load pressure 0-100N, load speed 100N / min, scratch rate 1mm / min, scratch length 1mm. The adhesion results are as follows: Figure 2 shown.

[0030] Comparative Example 1: The difference between this comparative example and Example 1 is that steps S3 and S4 are removed, and the second, third and fourth diamond coating deposition steps in step S5 are removed, that is, a layer of micron diamond coating is directly deposited on the surface of the surface pretreated alloy, and then the performance test of the prepared protective coating is carried out according to the performance test method in Example 1. The results are as follows: Figure 2 shown.

[0031] From the comparison of performance test results, it can be seen that by placing the pretreated cemented carbide in a vacuum tube furnace and pumping in a mixed gas of hydrogen and diborane for surface boronizing, and then placing it in a plasma surface alloying furnace for surface sputtering deposition of a tantalum layer, after reverse sputtering, four layers of diamond coating are deposited by chemical vapor deposition, so that the high-temperature resistant protective coating on the surface of the cemented carbide not only has good high-temperature resistance and corrosion resistance, but also has excellent adhesion and wear resistance, thereby achieving the effect of extending the service life of the cemented carbide.

[0032] Comparative Example 2: The difference between this comparative example and Example 1 is that only step S3 is removed, that is, a tantalum layer is directly deposited on the surface of the surface pretreated alloy, and then the performance test of the prepared protective coating is carried out according to the performance test method in Example 1. The results are as follows: Figure 2 shown.

[0033] From the comparison of performance test results, it can be seen that before chemical vapor deposition of diamond coating on the cemented carbide surface, the pre-treated cemented carbide surface is first subjected to vacuum hot boronizing treatment using diborane gas to generate Co-WB phase on the cemented carbide surface to prevent Co from diffusing into the diamond coating, thereby preventing Co from catalyzing the formation of non-diamond carbon at the interface between diamond and cemented carbide and affecting the interface and bonding force between diamond and cemented carbide, thereby achieving the effect of improving the adhesion of the diamond coating.

[0034] Comparative Example 3: The difference between this comparative example and Example 1 is that only step S4 is removed, that is, the diamond coating is directly deposited on the surface of the surface boronized alloy, and then the performance test of the prepared protective coating is carried out according to the performance test method in Example 1. The results are as follows: Figure 2 shown.

[0035] From the comparison of performance test results, it can be seen that after the boronizing treatment on the surface of the cemented carbide, a tantalum layer is deposited on the surface of the boronized layer to further inhibit the diffusion of Co into the diamond coating. In addition, the reverse sputtering process can form micropores on the surface of the tantalum layer, thereby improving the adhesion of the diamond coating to the tantalum layer, thereby achieving the effect of further improving the adhesion of the diamond coating.

[0036] Comparative Example 4: The difference between this comparative example and Example 1 is that the second, third and fourth diamond coating deposition steps in step S5 are removed, that is, only a layer of micron diamond coating with a thickness of 3 μm is deposited on the surface of the thin tantalum alloy layer, and then the performance test of the prepared protective coating is carried out according to the performance test method in Example 1. The results are as follows: Figure 2 shown.

[0037] From the comparison of performance test results, it can be seen that by gradually adjusting the methane flow rate, the four-layer micro-nano composite diamond coating prepared on the surface of the tantalum layer by chemical vapor deposition has high wear resistance and good adhesion, which can improve the poor adhesion of the single-layer nano-diamond coating and the high wear problem caused by the rough surface of the single-layer micron diamond coating.

[0038] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A process for preparing a high temperature resistant protective coating on a cemented carbide surface, characterized in that: The steps include: S1: Cleaning carbide, The YG type cemented carbide was immersed in acetone, deionized water and anhydrous ethanol in turn, and ultrasonically cleaned respectively to obtain a three-times cleaned alloy; S2: Etching and microwave plasma decarburization, The alloy cleaned three times is sequentially soaked in the first soaking liquid and the second soaking liquid for etching, and then subjected to surface sandblasting and microwave plasma decarburization to obtain a surface pretreated alloy; S3: Pump in diborane for surface boronization, Mixing hydrogen and diborane to form a boron-containing gas, then placing the surface pretreated alloy in a vacuum tube furnace, introducing the boron-containing gas, heating and pressurizing, and performing surface boriding to obtain a surface borided alloy; S4: Surface sputtering deposition of tantalum layer and reverse sputtering, The surface boride alloy is placed in a plasma surface alloying furnace, and a tantalum layer is sputtered and deposited on the surface of the surface boride alloy under heating and power supply conditions, and then reverse sputtering is performed to obtain a thin tantalum layer alloy; S5: Control the methane flow and chemically vapor deposit four layers of diamond coating, The thin tantalum layer alloy is placed in an acetone dispersion of diamond for ultrasonic oscillation, then ultrasonically cleaned with an ethanol solution, and then four layers of diamond coating are deposited on the surface of the thin tantalum layer alloy by chemical vapor deposition by controlling the methane flow rate to obtain a high-temperature resistant protective coating.

2. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 1, characterized in that: The cleaning of cemented carbide in step S1 specifically comprises the following steps: S1.1: Place the YG cemented carbide in an ultrasonic cleaning machine, add acetone to the ultrasonic cleaning machine until the YG cemented carbide is completely immersed, then start the ultrasonic cleaning machine and perform ultrasonic cleaning for 10-20 minutes to obtain a cleaned alloy; S1.2: Open the liquid outlet assembly of the ultrasonic cleaning machine, discharge the acetone, and then add deionized water to the ultrasonic cleaning machine until the primary cleaning alloy is completely immersed, and continue ultrasonic cleaning for 10-20 minutes to obtain a secondary cleaning alloy; S1.3: Open the liquid outlet assembly of the ultrasonic cleaning machine, discharge the deionized water, and then add anhydrous ethanol to the ultrasonic cleaning machine until the secondary cleaning alloy is completely immersed, and ultrasonically clean for 20-30 minutes to obtain the tertiary cleaning alloy.

3. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 2, characterized in that: The etching and microwave plasma decarburization in step S2 specifically includes the following steps: S2.1: placing the three-cleaned alloy obtained in step S1.3 in a soaking box, then pouring the first soaking liquid into the soaking box, soaking for 10-20 minutes, and performing an etching to obtain a first-etched alloy; S2.2: Open the liquid outlet valve of the immersion box to discharge the first immersion liquid, then pour the second immersion liquid into the immersion box, let it stand and soak for 10-20 minutes, and perform secondary etching on the above-mentioned primary etched alloy to obtain a secondary etched alloy; S2.3: Rinse the secondary etched alloy with deionized water for 2-3 minutes, and then sandblast the surface with diamond powder to obtain a textured alloy; S2.4: Place the above-mentioned textured alloy in a microwave chemical vapor deposition device, adjust the microwave power to 500-600W and the mixed gas pressure in the reaction chamber to 2-3kPa, etch the textured alloy for 1-2h for decarburization treatment, and obtain a surface pretreated alloy.

4. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 3, characterized in that: Step S3 of pumping diborane to perform surface boronization specifically includes the following steps: S3.1: Using a first gas pump to measure hydrogen, and using a second gas pump to measure diborane, then pumping the hydrogen and diborane into a mixing box at a volume ratio of 16-20:1 through the first gas pump and the second gas pump, and mixing them thoroughly to obtain a boron-containing gas; S3.2: placing the surface pretreated alloy obtained in step S2.4 in a vacuum tube furnace device, and then passing the boron-containing gas in the mixing box into the vacuum tube furnace device through the air inlet valve until the air pressure sensor in the vacuum tube furnace device detects that the air pressure in the furnace reaches 10-12 kPa; S3.3: Start the vacuum tube furnace equipment, heat the surface pretreated alloy at a temperature of 1000-1200° C. for 1-2 hours, and perform surface boriding on the surface pretreated alloy to obtain a surface borided alloy.

5. The process for preparing a high temperature resistant protective coating on a hard alloy surface according to claim 4, characterized in that: The surface sputtering deposition of the tantalum layer and reverse sputtering in step S4 specifically comprises the following steps: S4.1: placing the surface borided alloy obtained in step S3.3 in a plasma surface alloying furnace, and introducing argon gas into the furnace until all the air in the furnace is exhausted; S4.2: adjusting the heating temperature of the plasma surface alloying furnace to 800-900°C, the working voltage of the anode and cathode to 300-400V, and the working voltage of the source electrode to 600-750V; S4.3: starting the plasma surface alloying furnace, under the bombardment of argon ions, the source electrode sputters out tantalum ions, and deposits them on the surface of the surface boride alloy to obtain a thick tantalum alloy layer; S4.4: Adjust the working voltage of the anode and cathode to 600-750V and the working voltage of the source electrode to 300-450V, and start the plasma surface alloying furnace again. Under the action of the high voltage electric field, the argon ions move and bombard the surface of the thick tantalum layer alloy, and reverse sputter to obtain a thin tantalum layer alloy.

6. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 5, characterized in that: Step S5 of controlling the methane flow rate and chemically vapor depositing four layers of diamond coating specifically includes the following steps: S5.1: placing the thin tantalum alloy layer obtained in step S4.4 in a diamond acetone dispersion, ultrasonically vibrating for 30-40 minutes, and then placing it in an ethanol solution and ultrasonically cleaning for 3-5 minutes to obtain a prefabricated coating alloy; S5.2: placing the above prefabricated coating alloy in a chemical vapor deposition device, adjusting the hydrogen flow rate to 800-1000 mL / min, the heating temperature to 850-900°C and the methane flow rate to 20-25 mL / min, and depositing for 2-3 hours to obtain a single-layer diamond coating; S5.3: Keeping other conditions unchanged, adjust the methane flow rate to 25-30 mL / min, and continue deposition for 1-2 h to obtain a double-layer diamond coating; S5.4: Keeping other conditions unchanged, adjust the methane flow rate to 20-25 mL / min, and continue deposition for 2-3 h to obtain a three-layer diamond coating; S5.5: Keep other conditions unchanged, adjust the methane flow rate to 25-30 mL / min, and continue deposition for 1-2 hours to obtain a high temperature resistant protective coating.

7. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 3, characterized in that: The first soaking liquid is prepared by mixing potassium ferrocyanide, potassium hydroxide and deionized water in a mass ratio of 1:1:18-20, the second soaking liquid is prepared by mixing hydrochloric acid and hydrogen peroxide in a volume ratio of 1:4-6, and the mixed gas is a mixture of argon and hydrogen.

8. The process for preparing a high temperature resistant protective coating on a cemented carbide surface according to claim 4, characterized in that: During the high-temperature boriding process of the vacuum tube furnace equipment, when the air pressure sensor detects that the air pressure in the furnace is lower than 10kPa, the air pressure sensor sends a start signal to the controller. After the controller receives the start signal sent by the air pressure sensor, it controls the air intake valve to open and replenishes boron-containing gas into the vacuum tube furnace equipment until the air pressure sensor detects that the air pressure in the vacuum tube furnace equipment reaches 10-12kPa. The air pressure sensor sends a stop signal to the controller. When the controller receives the stop signal sent by the air pressure sensor, it controls the air intake valve to close and stops replenishing boron-containing gas. This cycle continues to maintain the internal air pressure of the vacuum tube furnace stable.

9. The process for preparing a high temperature resistant protective coating on a hard alloy surface according to claim 6, characterized in that: The total thickness of the diamond coating is 3-3.4 μm.

10. A high temperature resistant protective coating on a hard alloy surface, characterized in that: The coating is prepared by the process for preparing a high temperature resistant protective coating on the surface of a cemented carbide according to any one of claims 1 to 9.

Images